A beam sweeping mechanism is introduced in 5G New Radio (NR). Synchronization signals, minimum system information (MSI) and signals for the network to page UE (user equipment) required for an initial access of the UE to a cell are broadcast through the beam sweeping and cover the entire cell.
Currently, in the 5G NR standards, a synchronization signal and a PBCH (physical broadcast channel) carrying the basic system information are combined to constitute a SSB (synchronization signal block). Each of the SSBs carries a SSB index as an identifier. Random access signals sent by the UE for initial access or the like inform a 5G NodeB of the index of the SSB expected to access.
In a conventional technology, a mapping relationship between random access preambles and SSBs as well as that between random access channel resources and SSBs is assigned in the MSI, and the mapping relationship is given by a bitmap or a table.
However, the MSI space is limited, and the number of SSBs can be as many as 64. So that, the mapping relationship between random access preambles and SSBs as well as that between random access channel resources and SSBs requires large cost.